Putative catalytic domain, repeat 2, of Escherichia coli uncharacterized protein ymdC and similar proteins
Putative catalytic domain, repeat 2, of Escherichia coli uncharacterized protein ymdC and similar proteins. In Escherichia coli, there are two genes, f413 (ybhO) and o493 (ymdC), which are homologous to gene cls that encodes the Escherichia coli cardiolipin (CL) synthase. The prototype of this subfamily is an uncharacterized protein ymdC specified by the o493 (ymdC) gene. Although the functional characterization of ymdC and similar proteins remains unknown, members of this subfamily show high sequence homology to bacterial CL synthases, which catalyze the reversible phosphatidyl group transfer between two phosphatidylglycerol molecules to form CL and glycerol. Moreover, ymdC and its similar proteins contain two HKD motifs (H-x-K-x(4)-D, where x represents any amino acid residue) that characteriszes the phospholipase D (PLD) superfamily. The two motifs may be part of the active site and may be involved in phosphatidyl group transfer.
Comment:Based on similarity with phospholipase D, which functions as a bi-lobed monomer with two catalytic domains. Each domain carries one copy of the conserved HKD motif and two domains form a single active site.
Comment:The HKD signature motif (expanded to H-x-K-x(4)-D-x(6)-G-S-x-N, where x represents any amino acid residue) characterizes the PLD superfamily.
Comment:Most residues in the HKD motif are part of the active site.
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